May 3: A view of Usama bin Laden's compound in Abbottabad, Pakistan.
(AP)

Questions are being raised about the safety of a Pakistani doctor who might have played a vital, heroic -- and even unknowing -- role in the ultimate take-down of Usama bin Laden.

Dr. Shikal Afridi may be in the custody of Pakistan's clandestine Inter-Services Intelligence agency after it discovered that he had participated in a fake Hepatitis B vaccination program that attempted to gain DNA samples from people within the Abbottabad compound that housed bin Laden, several followers and their families.

Secretary of Defense Leon Panetta this week questioned the charges against Afridi.

"I'm very concerned about what the Pakistanis did with this individual," he told CBS News. "This was an individual who, in fact, helped provide intelligence on -- that was very helpful with regards to this operation. And he was not in any way treasonous towards Pakistan. He was not in any way doing anything that would have undermined Pakistan."

Panetta also underscored that the U.S. and Pakistan "have a common cause here against terrorism."

"And for them to take this kind of action against somebody who was helping to go after terrorism, I just think it's a real mistake on their part," said Panetta, who was head of the CIA at the time of the Navy SEALs raid last May.

His comments are the first to publicly acknowledge that Afridi was involved in the operation.

Afridi was arrested shortly after the raid and is thought to still be in custody despite not formally being charged with a crime. His detention has widened the rift between the U.S. and Pakistan, with Washington until now quietly pressing for his release so Afridi and his family can resettle in the U.S., according to The Guardian newspaper, which first reported on the doctor's role in the operation last July.

Reports suggest that Afridi rang the bell of the bin Laden compound during the vaccination drive, and the nurse who was with him was able to get inside but was ultimately unsuccessful in getting any DNA samples.

Reports have also suggested that Afridi may not have even been aware that he was working for the CIA and instead may have been recruited by other Pakistanis to carry out the fake house-to-house vaccination program.

Panetta also told CBS News that there was no actual evidence of Pakistani involvement in bin Laden's presence in Pakistan, but suspicions must have been raised.

"I personally have always felt that somebody must have had some sense of what was happening at this compound," he said.

"Don't forget, this compound had 18-foot walls around it -- 12-foot walls in some areas, 18-foot walls elsewhere, a seven-foot wall on the third balcony of the house. It was the largest compound in the area," he said. "So you would have thought that somebody would have asked the question, 'What the hell's going on there?'"

Perry Chiaramonte is a reporter for FoxNews.com. Follow him on Twitter at @perrych